Anthracnose

Anthracnose, a group of fungal diseases that affect a variety of plants in warm, humid areas. Shade trees such as sycamore, ash, oak, and maple are especially susceptible, though the disease is found in a number of plants, including grasses and annuals.

anthracnoseA rugosa rose plant infected with anthracnose.

Anthracnose causes the wilting, withering, and dying of tissues. It commonly infects the developing shoots and leaves. The causative fungi (usually Colletotrichum or Gloeosporium) characteristically produce spores in tiny, sunken, saucer-shaped fruiting bodies known as acervuli. Symptoms include sunken spots or lesions (blight) of various colours in leaves, stems, fruits, or flowers, and some infections form cankers on twigs and branches. The severity of the infection depends on both the causative agent and the infected species and can range from mere unsightliness to death.

In the late 1970s a new form of the disease, known as dogwood anthracnose, was identified in North America. Unlike other forms of anthracnose, it thrives in cool climates. Dogwood anthracnose first appeared in the Pacific Northwest and soon spread to the eastern United States, eventually resulting in severe losses to natural stands of dogwoods in mountainous regions. The causative agent, the fungus Discula destructiva, was not described until 1991.

Anthracnose can be avoided by destroying diseased parts, using disease-free seed and disease-resistant varieties, applying fungicides, and controlling insects and mites that spread anthracnose fungi from plant to plant. For infections of annual plants, such as tomatoes or melons, crop rotation is suggested to limit the accumulation of fungal spores in the soil.